U.S. patent application number 16/229164 was filed with the patent office on 2020-06-25 for electrostatic charging air cleaning device and collection electrode.
The applicant listed for this patent is Robert Bosch GmbH. Invention is credited to Jake CHRISTENSEN, Nathan CRAIG, Sondra HELLSTROM, Christina JOHNSTON, Saravanan KUPPAN, Michael METZGER.
Application Number | 20200197953 16/229164 |
Document ID | / |
Family ID | 71097297 |
Filed Date | 2020-06-25 |
United States Patent
Application |
20200197953 |
Kind Code |
A1 |
METZGER; Michael ; et
al. |
June 25, 2020 |
ELECTROSTATIC CHARGING AIR CLEANING DEVICE AND COLLECTION
ELECTRODE
Abstract
A method of forming a collection electrode for an electrostatic
charging air cleaning device. The method includes forming a slurry
including a carbon black powder material, a polymeric binder
material and a liquid solvent material. The method further includes
applying the slurry to a substrate material. The method also
includes curing the slurry to obtain a coating layer on the
substrate material to form the collection electrode.
Inventors: |
METZGER; Michael;
(Sunnyvale, CA) ; KUPPAN; Saravanan; (Sunnyvale,
CA) ; HELLSTROM; Sondra; (East Palo Alto, CA)
; CRAIG; Nathan; (Sunnyvale, CA) ; JOHNSTON;
Christina; (Sunnyvale, CA) ; CHRISTENSEN; Jake;
(Elk Grove, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Robert Bosch GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
71097297 |
Appl. No.: |
16/229164 |
Filed: |
December 21, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B03C 3/88 20130101; B03C
3/47 20130101; B03C 2201/32 20130101; B03C 3/70 20130101; B03C 3/12
20130101; B03C 3/011 20130101; B03C 3/53 20130101; B03C 3/41
20130101; B03C 3/60 20130101; B03C 3/51 20130101; B03C 3/38
20130101 |
International
Class: |
B03C 3/47 20060101
B03C003/47; B03C 3/88 20060101 B03C003/88; B03C 3/38 20060101
B03C003/38; B03C 3/53 20060101 B03C003/53 |
Claims
1. A method of forming a collection electrode for an electrostatic
charging air cleaning device, the method comprising: forming a
slurry including a carbon black powder material, a polymeric binder
material and a liquid solvent material; applying the slurry to a
substrate material; and curing the slurry to obtain a coating layer
on the substrate material to form the collection electrode.
2. The method of claim 1, wherein the applying step includes tape
casting or spraying the slurry onto the substrate material.
3. The method of claim 1, wherein the carbon black powder material
includes an electro-conductive carbon black material.
4. The method of claim 1, wherein the surface area of the carbon
black powder material is in a range of 800 to 1,200 m.sup.2/g for
N.sub.2 sorption.
5. The method of claim 1, wherein the polymeric binder material
includes polyvinylidene fluoride (PvDF).
6. The method of claim 1, wherein the liquid solvent material
includes n-methyl-2-pyrrolidone (NMP).
7. The method of claim 1, further comprising mechanically
perforating a metal sheet material to form the substrate
material.
8. The method of claim 1, wherein the substrate material is an
expanded metal material.
9. The method of claim 1, wherein the substrate material is a metal
mesh material.
10. A collection electrode for an electrostatic charging air
cleaning device, the collection electrode comprising: a substrate
material; and a coating layer coated onto the substrate material
and including a carbon black material and a polymeric binder.
11. The collection electrode of claim 10, wherein the carbon black
material includes an electro-conductive carbon black material.
12. The collection electrode of claim 10, wherein a surface area of
the carbon black material is in a range of 800 to 1,200 m.sup.2/g
for N.sub.2 sorption.
13. The collection electrode of claim 10, wherein the polymeric
binder includes polyvinylidene fluoride (PvDF).
14. The collection electrode of claim 10, wherein the substrate
material is an expanded metal material.
15. The collection electrode of claim 10, wherein the substrate
material is a metal mesh material.
16. An electrostatic charging air cleaning device comprising: a
pre-charger configured to generate a corona discharge to
electrostatically charge particulate matter (PM) in an air stream;
a separator downstream the pre-charger configured to convey the
electrostatically charged PM; and a collection electrode configured
to receive the conveyed electrostatically charged PM and to adsorb
the PM, the collection electrode including a substrate material and
a coating layer coated onto the substrate material and including a
carbon black material and a polymeric binder.
17. The electrostatic charging air cleaning device of claim 16,
wherein the carbon black material includes an electro-conductive
carbon black material.
18. The electrostatic charging air cleaning device of claim 16,
wherein a surface area of the carbon black material is in a range
of 800 to 1,200 m.sup.2/g for N.sub.2 sorption.
19. The electrostatic charging air cleaning device of claim 16,
wherein the polymeric binder includes polyvinylidene fluoride
(PvDF).
20. The electrostatic charging air cleaning device of claim 16,
wherein a voltage bias of the collection electrode is opposite the
wire-plate pre-charger.
21. A computer system for calculating an amount of particulate
matter occupying a surface area of a collection electrode of an
electrostatic charging air cleaning device including a computer
having a processor for executing computer-executable instructions
and a memory for maintaining the computer-executable instructions,
the computer-executable instructions when executed by the processor
perform the following functions: receiving data indicative of a
current flow between a separator and the collection electrode of
the electrostatic charging air cleaning device; and determining the
amount of particulate matter occupying the surface area of the
collection electrode based on the data indicative of the current
flow.
22. The computer system of claim 21, wherein the
computer-executable instructions when executed by the processor
performs the further function of performing the receiving step over
time to obtain data indicative of current flow over time between
the separator and the collection electrode of the electrostatic
charging air cleaning device.
23. The computer system of claim 22, wherein the
computer-executable instructions when executed by the processor
performs the further function of predicting a maintenance state of
the collection electrode based on the data indicative of the
current flow over time.
24. The computer system of claim 23, wherein the maintenance state
is cleaning the collection electrode.
25. The computer system of claim 23, wherein the maintenance state
is replacing the collection electrode.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an electrostatic charging
air cleaning device and collection electrode, and in some
embodiments, an electrostatic precipitation (ESP) air cleaning
device having a relatively high surface area collection
electrode.
BACKGROUND
[0002] Non-limiting examples of typical air pollutants are
particulate matter (PM) of different sizes, gases, volatile organic
compounds (VOCs), bacteria and viruses, and odors. The size of
particulate matter is typically measured by particles with x .mu.m
diameter (PMx), where x may be 2.5, 5, 10, etc. Examples of
pollutant gases include, without limitation, CO.sub.2, CO, NO.sub.x
and SO.sub.x. Examples of VOCs include, without limitation,
methane, benzene, ethylene glycol, formaldehyde, methylene
chloride, tetrachloroethylene, toluene, xylene, and
1,3-butadiene.
[0003] Many conventional technologies have been used for removing
pollutants from the air. These technologies include high-efficiency
particle arresting (HEPA) filtration, activated carbon filters, air
ionizers, and electrostatic precipitators (ESP). Each of these
technologies have strengths and weaknesses that make them more or
less suitable for certain applications (e.g., indoor versus outdoor
cleaning). Some of the characteristics commonly used to measure the
performance of air cleaning technologies include clean air delivery
rate (CADR) (in units of m.sup.3/h), noise level (in dB), and costs
per volume of air purified ($/m.sup.3).
[0004] HEPA filters are commonly utilized to purify air in homes,
office buildings and car interiors. HEPA filters are relatively
cost effective and efficient for removing PM with a minimum
efficiency of 99.97% removal of PM0.3 and larger. However, HEPA
filters have difficulties removing VOCs from air and certain gases,
such as NO.sub.x and CO cannot be filtered. Moreover, bio fouling
of the filter membranes may cause health risks. Additionally,
clogging may lead to frequent filter replacement (about every six
(6) months).
SUMMARY
[0005] According to one embodiment, a method of forming a
collection electrode for an electrostatic charging air cleaning
device is disclosed. The method includes forming a slurry including
a carbon black powder material, a polymeric binder material and a
liquid solvent material. The method further includes applying the
slurry to a substrate material. The method also includes curing the
slurry to obtain a coating layer on the substrate material to form
the collection electrode.
[0006] According to another embodiment, a collection electrode for
an electrostatic charging air cleaning device is disclosed. The
collection electrode includes a substrate material, and a coating
layer coated onto the substrate material and including a carbon
black material and a polymeric binder.
[0007] In yet another embodiment, an electrostatic charging air
cleaning device is disclosed. The device includes a wire-plate
pre-charger configured to generate a corona discharge to
electrostatically charge particulate matter (PM) in an air stream,
a separator downstream the wire-plate pre-charge configured to
convey the electrostatically charged PM, and a collection electrode
configured to receive the conveyed electrostatically charged PM and
to adsorb the PM. The collection electrode includes a substrate
material and a coating layer coated onto the substrate material.
The coating layer includes a carbon black material and a polymeric
binder.
[0008] In a fourth embodiment, a computer system for calculating an
amount of particulate matter occupying a surface area of a
collection electrode of an electrostatic charging air cleaning
device is disclosed. The computer system includes a computer having
a processor for executing computer-readable instructions and a
memory for maintaining the computer-executable instructions. The
computer-executable instructions when executed by the processor
perform the following functions: receiving data indicative of a
current flow between a separator and the collection electrode of
the electrostatic charging air cleaning device; and determining the
amount of particulate matter occupying the surface area of the
collection electrode based on the data indicative of the current
flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a schematic diagram of an electrostatic
precipitation (ESP) air filter assembly according to an
embodiment.
[0010] FIG. 2 depicts a perspective view of discharge electrodes
dispersed between discharge plates according to an embodiment.
[0011] FIG. 3 is a perspective view of a discharge electrode and an
adjacent discharge plate according to one embodiment.
DETAILED DESCRIPTION
[0012] Embodiments of the present disclosure are described herein.
It is to be understood, however, that the disclosed embodiments are
merely examples and other embodiments can take various and
alternative forms. The figures are not necessarily to scale; some
features could be exaggerated or minimized to show details of
particular components. Therefore, specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the embodiments. As those of
ordinary skill in the art will understand, various features
illustrated and described with reference to any one of the figures
can be combined with features illustrated in one or more other
figures to produce embodiments that are not explicitly illustrated
or described. The combinations of features illustrated provide
representative embodiments for typical applications. Various
combinations and modifications of the features consistent with the
teachings of this disclosure, however, could be desired for
particular applications or implementations.
[0013] Except in the examples, or where otherwise expressly
indicated, all numerical quantities in this description indicating
amounts of material or conditions of reaction and/or use are to be
understood as modified by the word "about" in describing the
broadest scope of the invention. Practice within the numerical
limits stated is generally preferred. Also, unless expressly stated
to the contrary: percent, "parts of," and ratio values are by
weight; the term "polymer" includes "oligomer," "copolymer,"
"terpolymer," and the like; the description of a group or class of
materials as suitable or preferred for a given purpose in
connection with the invention implies that mixtures of any two or
more of the members of the group or class are equally suitable or
preferred; molecular weights provided for any polymers refers to
number average molecular weight; description of constituents in
chemical terms refers to the constituents at the time of addition
to any combination specified in the description, and does not
necessarily preclude chemical interactions among the constituents
of a mixture once mixed; the first definition of an acronym or
other abbreviation applies to all subsequent uses herein of the
same abbreviation and applies mutatis mutandis to normal
grammatical variations of the initially defined abbreviation; and,
unless expressly stated to the contrary, measurement of a property
is determined by the same technique as previously or later
referenced for the same property.
[0014] This invention is not limited to the specific embodiments
and methods described below, as specific components and/or
conditions may, of course, vary. Furthermore, the terminology used
herein is used only for the purpose of describing particular
embodiments of the present invention and is not intended to be
limiting in any way.
[0015] As used in the specification and the appended claims, the
singular form "a," "an," and "the" comprise plural referents unless
the context clearly indicates otherwise. For example, reference to
a component in the singular is intended to comprise a plurality of
components.
[0016] The term "substantially" or "about" may be used herein to
describe disclosed or claimed embodiments. The term "substantially"
or "about" may modify a value or relative characteristic disclosed
or claimed in the present disclosure. In such instances,
"substantially" or "about" may signify that the value or relative
characteristic it modifies is within .+-.0%, 0.1%, 0.5%, 1%, 2%,
3%, 4%, 5% or 10% of the value or relative characteristic.
[0017] An emerging technology for air cleaning is electrostatic
precipitation (ESP). ESP uses an ionization electrode (for example,
one or more wires) to electrostatically charge particle suspended
in an airflow. Subsequently, the trajectories of the charged
particles are distorted by an induced electric field toward a
collection electrode (for example, an electronically conducting
collecting plate). The electrostatically adsorbed particles are
trapped at the collection electrode, provided that a voltage bias
is applied between the ionization electrode and the collection
electrode. The trapped, adsorbed particles are consequently removed
from the air stream using a collection electrode, for example. The
collection electrode is typically a metal plate. The metal plate
needs periodic maintenance, e.g., washing the collection electrode,
in a frequency similar to filter replacement requirements for
HEPA.
[0018] In light of the foregoing, what is needed is a high surface
area collection electrode for an electrostatic charging air
cleaning system, such as an ESP. What is also needed is a method
for manufacturing a high surface area collection electrode and an
air cleaning device including the high surface area collection
electrode.
[0019] In one embodiment, a collection electrode of an ESP device
may be formed. In a first step, high surface area carbon black
powder is dispersed into a liquid solvent. The high surface area
carbon black powder may include an electro-conductive carbon black
material such as Ketjenblack. The percentage of the
electro-conductive carbon black material in the carbon black powder
may be one of the following values or within a range of any two of
the following values: 60, 65, 70, 75, 80 and 85 percent by weight.
The surface area of the carbon black powder may be one of the
following values or within a range of any two of the following
values: 800, 900, 1,000, 1,100 and 1,200 m.sup.2/g for N.sub.2
sorption. The liquid solvent may be n-methyl-2-pyrrolidone (NMP).
Other suitable, non-limiting solvents include water, isopropanol
(IPA), cyclohexanone ((CH.sub.2).sub.5CO), dimethyl ether (DME) and
acetonitrile (MeCN).
[0020] In a second step, a polymer binder is added to the carbon
black liquid solvent solution to form a carbon black polymer binder
slurry. The polymer binder may include a binder material, such as
polyvinylidene fluoride (PvDF). Other suitable, non-limiting
polymer binder material include polytetrafluoroethylene (PTFE),
perfluoroalkoxy (PFA), tetrafluorethylene-perfluoropropylene (FEP),
carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR).
The percentage of binder material in the polymer binder may be one
of the following values or within a range of any two of the
following values: 15, 20, 25, 30, 35 and 40 percent by weight. In
another step, the slurry is tape cast onto a substrate material.
Alternatively, an air brush may be utilized to spray the slurry
onto the substrate material. The substrate material may be a metal
foil or metal mesh material. The metal foil material may be an
expanded stainless steel foil. The shape of the apertures formed by
the expanding process may be generally rectangular. The nominal
size of the apertures of the expanded material may be one of the
following values or within a range of any two of the following
values: 10 .mu.m, 50 .mu.m, 100 .mu.m, 200 .mu.m and 500 .mu.m. The
metal mesh material may be a woven stainless steel mesh. The shape
of the apertures formed by the strands of mesh may be generally
rectangular or have an irregular shape. The nominal size of the
apertures of the woven mesh material may be one of the following
values or within a range of any two of the following values: 10
.mu.m, 50 .mu.m, 100 .mu.m, 200 .mu.m and 500 .mu.m. The thickness
of the substrate material may be one of the following values or
within a range of any two of the following values: 16, 18, 20, 22
and 24 .mu.m. In one or more embodiments, the substrate material is
mechanically perforated before being coated with the carbon black
liquid solvent solution with the polymeric binder material. The
nominal size of the apertures formed by the mechanical perforations
may be one of the following values or within a range of any two of
the following values: 10 .mu.m, 50 .mu.m, 100 .mu.m, 200 .mu.m and
500 .mu.m.
[0021] In the next step according to certain embodiments, the
solvent is evaporated from the mixture coated onto the current
collector material to obtain a collection electrode. The
evaporation step can be performed at an average temperature for a
period of time at atmospheric pressure conditions. The average
temperature may be one of the following values or within a range of
any two of the following values: 70, 80, 90, 100, 110, 120, 130 and
140.degree. C. The period of time may be one of the following
values or within a range of any two of the following values: 2,
2.5, 3, 3.5 and 4 hours. The resulting collection electrode may
have a porosity of one of the following values or within a range of
any two of the following values: 40, 45, 50, 55, 60, 65 and 70
percent. The resulting collection electrode may have a thickness of
any one of the following values or within a range of any two of the
following values: 200, 250, 300, 350, and 400 .mu.m. The surface
area of the resulting collection electrode may be one of the
following values or within a range of any two of the following
values: 800, 900, 1,000, 1,100 and 1,200 m.sup.2/g for N.sub.2
sorption.
[0022] In certain embodiments, nano- or micro-sized metallic
particles are used instead of high surface area carbon black
powder. Non-limiting examples of metallic particles may include
alloyed or atomic TiC, Ti, Ag, and Au. The concentration of the
metallic particles in the liquid solvent dispersion may be one of
the following values or within a range of any two of the following
values: 50, 60, 70, 80 and 90 percent.
[0023] The resulting collection electrode may be subjected to micro
structuring using an external force. Non-limiting examples of
external forces are mechanical or thermal. An example of a
mechanical external force is perforation with a needle to obtain
perforations in the collection electrode. The nominal radius of the
perforations may be one of the following values or within a range
of any two of the following values: 100 .mu.m, 100 .mu.m, 200
.mu.m, 500 .mu.m and 1 mm. An example of a thermal external force
is patterning the collection electrode with a laser beam.
[0024] FIG. 1 is a schematic diagram of an electrostatic
precipitation (ESP) filter assembly 10 according to an embodiment.
In one embodiment, the ESP filter assembly 10 has a rectangular
construction. The height and length dimensions of the ESP filter
assembly 10 are depicted by the letters H and L on FIG. 1. The
width of the ESP filter assembly 10 is coming into and out of the
page showing FIG. 1. The height may be any one of the following
values or within a range of any two of the following values: 10,
20, 50, 100, 200 and 500 cm. The length may be any one of the
following values or within a range of any two of the following
values: 5, 7, 10, 20, 30 and 50. The width of the ESP filter
assembly 10 may be any one of the following values or within a
range of any two of the following values: 10, 20, 50, 100, 200 and
500 cm. The ESP filter assembly 10 may be housed in a housing (not
shown), which may be formed of plastic.
[0025] ESP filter assembly 10 includes a pre-filter membrane 12.
The pre-filter membrane 12 is configured to preclude large
particles (e.g., dust particles) in an air stream 14 from entering
the ESP filter assembly 10. The size of the large particles may be
one of the following values or within a range of any two of the
following values: PM100, PM50, PM10, PMS, PM2.5 or very large dust
agglomerates. In one embodiment, the pre-filter membrane 12 is
formed of a porous polypropylene material. The porosity of the
pre-filter membrane may be one of the following values or within a
range of any two of the following values: 20, 40, 60 and 80
percent.
[0026] After exiting the pre-filter membrane 12, the air stream 14
enters a pre-filter chamber 16. The pre-filter chamber 16 is
configured to collect particulate matter within the air stream 14
before it enters pre-charger subassembly 20. The air within
pre-filter chamber 16 may include particulate matter of PM2.5 and
smaller. The concentration of particulate matter within the
pre-filter chamber 16 may be one of the following values or within
a range of any two of the following values: 40, 50, 60, 70, 80, 90,
100, 150, 200 and 300 .mu.g/m.sup.3. The length of pre-filter
chamber 16 may be one of the following values or within a range of
any two of the following values: 8, 9, 10, 11 and 12 cm.
Pre-charger subassembly 20 is configured to electrostatically
charge the particulate matter in the pre-filter chamber 16.
[0027] In the embodiment shown in FIG. 1, pre-charger subassembly
20 includes discharge electrodes 22, discharge plates 24, and
wiring 25 connected to discharge electrodes 22. FIG. 2 depicts a
perspective view of discharge electrodes 22 and discharge plates
24. In one embodiment, as shown in FIG. 2, each discharge electrode
22 is a wire and each discharge plate 24 is a rectangular plate. As
shown in FIG. 2, each discharge electrode wire is adjacent to a
pair of discharge plates 24. In one embodiment, plates 24 are
parallel to each other and are parallel to the axis of the adjacent
discharge electrode wire 22, which extends within the space created
by the pair of adjacent discharge plates 24 along the axis of the
adjacent discharge electrode wire 22 in a direction of the length
of each plate 24. Each wire 22 may be equally spaced between the
pair of adjacent plates 24. The spacing may be any one of the
following values or within a range of any two of the following
values: 10 .mu.m, 50 .mu.m, 100 .mu.m, 500.mu., 1 mm, 5 mm and 1
cm. As shown in FIGS. 1 and 2, discharge electrodes 22 are
connected in parallel to high voltage supply 26. The voltage
applied to discharge electrodes 22 may be any one of the following
values or within a range of any two of the following values: 1, 2,
5, 10, 20, 50 and 100 kV. As shown in FIGS. 1 and 2, discharge
plates 24 are connected to ground 28.
[0028] As shown by air stream 30, polluted air with particulate
matter 18 flows through discharge plates 24. Particulate matter 18
is not charged before entering the space between the discharge
plates 24. The velocity of the particulate matter flowing between
discharge plates 24 may be one of the following values or within a
range of any two of the following values: 0.1, 0.5, 1, 2, 5, 10,
20, 50 and 100 m/s. An electric field between each discharge
electrode 22 and pair of adjacent discharge plates creates a corona
discharge 32, as shown in FIG. 3. FIG. 3 is a perspective view of a
discharge electrode 22 and an adjacent discharge plate 24.
[0029] Particulate matter 18 entering pre-charger subassembly 20 is
charged by interaction with gaseous ions within the corona
discharge 32 to obtain charged particulate matter 34. A separation
of charge carriers in the electronic field occurs between a
discharge electrode 22 and adjacent discharge plates 24 such that
electrons go to the positive electrode (i.e., discharge plates 24)
and gaseous ions are repelled.
[0030] The length of each of the discharge plates 24 may be
relatively short to avoid precipitation of the charged particulate
matter 34. The length of the discharge plates 24 may be one of the
following values or within a range of any two of the following
values: 14, 16, 18, 20 and 22 .mu.m. The length of the discharge
electrodes 22 may be one of the following values or within a range
of any two of the following values: 14, 16, 18, 20 and 22
.mu.m.
[0031] The charged particulate matter 34 exits the pre-charger
subassembly 20 and enters a separator 36. Separator 36 is
configured to electrically insulate the pre-charger subassembly 20
from collection electrode 38 without impeding the diffusion of
pre-charged particulate matter 34 through separator 36. Separator
36 can be formed of a relatively high porosity, insulative
material. In one embodiment, separator 36 may be formed from a
glass fiber membrane. Other material suitable for use as separator
36 include, without limitation, polypropylene, PTFE and ceramic
wool. The length (thickness) of separator 36 may be one of the
following values or within a range of any two of the following
values: 400, 450, 500, 550 and 600 .mu.m. The porosity of separator
36 may be one of the following values or within a range of any two
of the following values: 75, 80, 85, 90 and 95 percent.
[0032] As depicted by arrows 40, pre-charged particulate matter 34,
which carries one or more positive charges, is accelerated towards
collection electrode 38 because it is polarized with a voltage bias
opposite pre-charger subassembly 20. As shown in FIG. 1, collection
electrode 38 is charged positively and pre-charger subassembly 20
is charged negatively. In one embodiment, upon impact on the
surface of the negatively charged collection electrode 40,
pre-charged particulate matter 34 loses its static positive charge
and becomes neutral. The length (thickness) of collection electrode
38 may be one of the following values or within a range of any two
of the following values: 200, 250, 300, 350, and 400 .mu.m. A
stream 54 of clean air exits ESP filter assembly 10. The clean air
stream 54 does not include the particulate matter particles 42
trapped by collection electrode 38.
[0033] Through multiple uses of ESP filter assembly 10, an
increasing percentage of the surface of collection electrode 38 is
occupied by particulate matter particles 42. Because collection
electrode 38 is formed of a relatively high surface area material
and has a relatively high porosity as disclosed in one or more
embodiments, the use of a single collection electrode 38 can be
repeated with a relatively high number of particulate matter
particles before collection electrode 38 becomes clogged and needs
to be replaced.
[0034] As shown in FIG. 1, current flow loop 44 connects separator
36 and collection electrode 38. Current flow sensor 46 is located
on current flow loop 44. Current flow sensor 46 is configured to
measure the current flow (e.g., amperes (A) over time to calculate
charge via Q(C)=I(A)/t(s)) from separator 36 to collection
electrode 38. This measured current flow represents the transfer of
electrons to particulate matter particles 42 due to the interaction
between positively charged pre-charged particulate matter 34 and
the negatively charged collection electrode 38. The data from
current flow sensor 46 is sent to controller 48, which is
configured to receive the current flow data. Controller 48 is
further configured to determine a state-of-charge value of
collection electrode 48. Controller 48 is further configured to
determine the amount of the surface area of collection electrode 48
occupied by adsorbed particles relative to the overall surface area
of collection electrode 48. Controller 48 may be configured to
output adsorbed particle accumulation data over time. This process,
method and algorithm can be used to predict need for maintenance,
for instance, collection electrode cleaning or replacement. In one
embodiment, controller 48 is in communication with memory 50 and
non-volatile storage 52. Memory 50 may be configured to store
current flow data. Non-volatile storage 52 may be configured to
store look up or correlation tables to covert current flow data
into adsorbed particle collection data. Non-volatile storage 52 may
be further configured to store adsorbed particle collection data
over time.
[0035] Controller 48 (or other processor as described herein) may
be configured to determine the collection capacity of collection
electrode 38. These determinations may use values and functional
relationships stored in non-volatile storage 52. The collection
capacity of collection electrode 38 can be estimated based on
typical concentrations of PM in a polluted air stream. The typical
PM concentration is any one of the following values or within a
range of any two of the following values: 80, 90, 100, 110 and 120
.mu.g/m.sup.3. An average density can be utilized to calculate a PM
concentration by volume (e.g., parts per billion (ppm)). For
example, if the PM concentration is 100 .mu.g/m.sup.3 and the
average density is 2 g/cm.sup.3, then the PM concentration by
volume is 0.05 ppb (100 .mu.g/m.sup.3/2 g/cm.sup.3). Accordingly, a
600 ft.sup.2 apartment contains 20 mg of PM. In one example, the
thickness of collection electrode is 200 .mu.m, which results in a
collection electrode volume of 0.02 cm.sup.3 per cm.sup.2 of
collection electrode. The void volume in the collection electrode
may be one of or within a range of any two of the following values:
30, 40, 50, 60 and 70 percent void volume. The maximum amount of PM
occupying the void volume before clogging may be one of or within a
range of any two of the following values: 40, 45, 50, 55 and 60
percent. In one example, using a void volume of 50 percent and a
maximum amount of PM occupation of 50 percent, the collection
capacity may be estimated as 10 mg PM per cm.sup.2 of geometric
collection electrode area (0.5.times.0.5.times.0.02
cm.sup.3.times.2 g/cm.sup.3).
[0036] An estimation of associated capacity assuming a PM size and
single positive charge may be calculated according to a process of
one or more embodiments. These estimations can be conducted for any
PM size, e.g., PM2.5 particles. In another example, the estimation
can be calculated for PM10 particles. The mass of PM10 particle of
may be estimated according to the following equation:
m = 4 3 r 3 .pi. .times. 2 g c 3 = 10 - 6 mg ( 1 ) ##EQU00001##
[0037] Accordingly, 1 cm.sup.2 of collection electrode area is
capable of adsorbing n=10.sup.7 PM10 particles. The associated
capacity assuming a single positive charge is calculated according
to the following equation:
Q = nF N A = 10 - 12 C per cm 2 electrode ( 2 ) ##EQU00002##
[0038] where n equals the number of particles (here, e.g., 10.sup.7
PM10 particles), F equals the Faraday constant (96 485.3329 C/mol),
and NA equals the Avogadro constant (6.02214086.times.10.sup.23
mol.sup.-1).
[0039] In another example, ESP air cleaning metrics can be
estimated for a device that has an active electrode area of at
least 1 m.sup.2. The following table identifies several metrics,
their calculations and the resulting values for an active electrode
area of at least 1 m.sup.2.
TABLE-US-00001 Metric Calculation Value Total mass of 10
mg/cm.sup.2 .times. 10.sup.4 cm.sup.2 100 g PM collected Total
particles 10.sup.7 particles/cm.sup.2 .times. 10.sup.4 cm.sup.2
10.sup.11 particles collected Total capacity 10.sup.-12 C./cm.sup.2
.times. 10.sup.4 cm.sup.2 10.sup.-8 C. (single charges)
[0040] In extending this example, a suitable air cleaner may clean
the air in a 600 ft.sup.2 apartment in 1 hour, which results in a
clean air delivery rate (CADR) of 165 m.sup.3/h, assuming a 3 m
room height. Using a PM pollution level of 100 .mu.g/m.sup.3, the
PM mass in that air volume would amount to 165 m.sup.3.times.100
.mu.g/m.sup.3 20 mg. Comparing this to an estimated collection
capacity of 100 mg, 1 hour of operation at a relatively high
pollution level of 100 .mu.g/m.sup.3 results in the utilization of
20 mg/100 g=0.02% of the collection capacity. Therefore, ESP filter
assembly 10 having a high surface area collection electrode 38
according to one or more embodiments may be operated for 5,000
hours, which is 60% of a year at a continuous (very high) pollution
level of 100 .mu.g/m.sup.3, without the need for replacement or
maintenance. In one or more embodiments, ESP filter assembly 10
having a high surface area collection electrode 38 may operate for
3 to 5 years without maintenance in regions with temporary high
pollution levels.
[0041] The controller 48 may include one or more devices selected
from microprocessors, micro-controllers, digital signal processors,
microcomputers, central processing units, field programmable gate
arrays, programmable logic devices, state machines, logic circuits,
analog circuits, digital circuits, or any other devices that
manipulate signals (analog or digital) based on computer-executable
instructions residing in memory 50. The memory 50 may include a
single memory device or a number of memory devices including, but
not limited to, random access memory (RAM), volatile memory,
non-volatile memory, static random access memory (SRAM), dynamic
random access memory (DRAM), flash memory, cache memory, or any
other device capable of storing information. The non-volatile
storage 52 may include one or more persistent data storage devices
such as a hard drive, optical drive, tape drive, non-volatile solid
state device, cloud storage or any other device capable of
persistently storing information.
[0042] The following application is related to the present
application: U.S. patent application Ser. No. ______ (RBPA 0123
PUS), filed on Dec. 21, 2018, which is incorporated by reference in
its entirety herein.
[0043] The program code embodying the algorithms and/or
methodologies described herein is capable of being individually or
collectively distributed as a program product in a variety of
different forms. The program code may be distributed using a
computer readable storage medium having computer readable program
instructions thereon for causing a controller or processor to carry
out aspects of one or more embodiments. Computer readable storage
media, which is inherently non-transitory, may include volatile and
non-volatile, and removable and non-removable tangible media
implemented in any method or technology for storage of information,
such as computer-readable instructions, data structures, program
modules, or other data. Computer readable storage media may further
include RAM, ROM, erasable programmable read-only memory (EPROM),
electrically erasable programmable read-only memory (EEPROM), flash
memory or other solid state memory technology, portable compact
disc read-only memory (CD-ROM), or other optical storage, magnetic
cassettes, magnetic tape, magnetic disk storage or other magnetic
storage devices, or any other medium that can be used to store the
desired information and which can be read by a computer. Computer
readable program instructions may be downloaded to a computer,
another type of programmable data processing apparatus, or another
device from a computer readable storage medium or to an external
computer or external storage device via a network.
[0044] Computer readable program instructions stored in a computer
readable medium may be used to direct a computer, other types of
programmable data processing apparatus, or other devices to
function in a particular manner, such that the instructions stored
in the computer readable medium produce an article of manufacture
including instructions that implement the functions, acts, and/or
operations specified in the flowcharts or diagrams. In certain
alternative embodiments, the functions, acts, and/or operations
specified in the flowcharts and diagrams may be re-ordered,
processed serially, and/or processed concurrently consistent with
one or more embodiments. Moreover, any of the flowcharts and/or
diagrams may include more or fewer functions than those illustrated
consistent with one or more embodiments.
[0045] While exemplary embodiments are described above, it is not
intended that these embodiments describe all possible forms
encompassed by the claims. The words used in the specification are
words of description rather than limitation, and it is understood
that various changes can be made without departing from the spirit
and scope of the disclosure. As previously described, the features
of various embodiments can be combined to form further embodiments
of the invention that may not be explicitly described or
illustrated. While various embodiments could have been described as
providing advantages or being preferred over other embodiments or
prior art implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics can be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes can
include, but are not limited to cost, strength, durability, life
cycle cost, marketability, appearance, packaging, size,
serviceability, weight, manufacturability, ease of assembly, etc.
As such, to the extent any embodiments are described as less
desirable than other embodiments or prior art implementations with
respect to one or more characteristics, these embodiments are not
outside the scope of the disclosure and can be desirable for
particular applications.
* * * * *